these heads have 167 runners, 2.02/1.60 valves, at least that is what the web site said when I looked up the part number. they may be comparable to vortec heads. I think they are better suited for an oval track car, but they came off a 406 that ran high 12's. the rockers are the high energy comp rockers as far as I can tell. I will throw in a low mileage cam and lifters, 305h comp, .525/.525 lift I think.